Low voltage AC (alternating current) contactors are used in industrial and commercial applications to control power flow to electrical loads in circuits operating up to about 600 V RMS. Such electrical contactors typically have one or more contact pads disposed on a moveable pad carrier (or bridge) structure that is selectively moved between an open and a closed position. The pad carrier is typically driven by a solenoid acting in opposition to a spring such that the bridge contacts can make and break contact, depending on the bridge position, with corresponding stationary contacts. The voltage supply and load supply leads are attached to respective contacts so that when the pad carrier is moved such that the bridge contact pads are disposed in contact with the respective stationary contact pads the circuit is closed; to open the circuit the pad carrier assembly is moved to separate the bridge contact pads from the respective stationary contact pads.
One source of wear on contactor devices is "bouncing" that occurs when the contact pads are moved to the closed position, which normally results from rapidly displacing one contact pad from the open to the closed position. It is desirable that the movable contact pad be disposed in physical contact with the other contact pad as rapidly as possible so as to minimize the chance of arcing between the contact pads that might occur if the pads are moved slowly together. The rapid closure often results in the pad bouncing, that is, repeatedly physically touching and moving off of the other pad, over a period of a few milliseconds as it settles into the closed state. The bouncing of the contacts, and the arcing between contacts as they open slightly during the bounce, contribute to erosion of the contacts. Typically the contactor device includes a mechanical apparatus to reduce contact bounce, such as springs or dampers to decelerate the relay plunger near the end of travel. Such mechanical apparatus are not completely successful in eliminating bounce upon closure and often require periodic adjustment and replacement.
Contact bouncing results in increased wear on the contact pads from the mechanical action of the multiple closures and also from the electrical arcing that occurs when the contact pads physically separate during bounces. It is thus desirable to eliminate bouncing altogether in an electrical contactor.